Lifelong antiretroviral therapy (ART) presents formidable problems. Therefore, among the many important goals for future HIV research is the development of temporally contained therapies capable of eradicating HIV infection. The persistence of quiescent HIV infection within a small population of long-lived CD4+ T cells is currently a major obstacle to the eradication of HIV infection. Human transcription factors recruit histone deacetylases (HDACs) to the HIV long terminal repeat promoter, mediating the formation of condensed heterochromatin, resulting in repression of LTR expression and viral production. Studies of the weak HDAC inhibitor valproic acid failed to measure a consistent depletion of resting cell infection in patients on ART, but this effect is far downstream of the primary molecular mechanism of HDAC inhibitors. We have demonstrated the ability of the potent inhibitor licensed for use in oncology, suberoylanilide hydroxamic acid (Vorinostat, VOR), selective for Class I HDACs, to induce HIV promoter expression in cell lines and virus production from the resting CD4+ T cells of antiretroviral-treated, aviremic HIV-infected patients. We propose a proof-of-principal study to measure the potential of potent HDAC inhibitors to induce the expression of persistent proviral HIV in vivo. Specific Aim 1: The frequency of detectable HIV RNA expression within resting CD4-- T cells will increase after VOR exposure in vivo: We will compare HIV RNA expression within resting CD4+ cells in HIV-infected patients on stable ART before and after VOR dosing. Specific Aim 2: Limited dosing of VOR in combination with ART to patients with HIV-1 infection will be safe and tolerable: We will characterize the safety, tolerability and spectrum of side effects of VOR in adult patients with HIV-1 infection receiving combination antiretroviral therapy. Although the goal of eradication of HIV infection is a distant one, this project may validate the ability of HDAC inhibitors to contribute to the purging of persistent infection and establish a new paradigm for early phase human testing of such approaches. RELEVANCE (See instructions): If eradication of virus from HIV-infected individuals is ever to be achieved, therapies that disrupt latent infection of resting CD4+ T-lymphocytes must be developed. Histone deacetylase (HDAC) inhibitors disrupt latent proviral infection ex vivo. We will directly assess the effect of HDAC inhibitors on HIV latency in vivo.